Single-layer graphene oxide dissociation dispersion method

Abstract

The invention provides a single-layer graphene oxide dissociation and dispersion method, and belongs to the technical field of graphene slurry preparation. The preparation method comprises the following steps: mixing crystalline flake graphite with an oxidizing agent, oxidizing, and then carrying out electrochemical intercalation stripping treatment to obtain graphene oxide microchips dispersed in an electrolyte for later use; s2, adding the graphene oxide nanoplatelets prepared in the step S1 into an organic solvent containing a catalyst for catalysis to obtain a graphene oxide catalytic solution for later use; in the graphene oxide slurry prepared in the invention, the single-layer rate is higher than 90%, and the solid content is obviously higher than about 4 wt.% in the industry; the graphene oxide is homogeneously dispersed and has no aggregate; the viscosity of the graphene oxide slurry is effectively controlled within an ideal range, the graphene oxide slurry has good flow ductility, and automatic pipeline conveying and coating can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of graphene slurry preparation, and in particular relates to a method for dissociating and dispersing a single-layer graphene oxide. Background Art

[0002] In 2004, the AK Geim team at the University of Manchester in the UK prepared graphene for the first time by mechanically exfoliating graphite, and further characterized various basic properties of graphene materials. In 2010, Geim and Novoselov were awarded the Nobel Prize in Physics for their research. A single layer of graphene is a two-dimensional crystal with a thickness of only 1000 Å. Before graphene was discovered, the physics community generally believed that long-range ordered one-dimensional or two-dimensional crystalline materials did not exist. Transmission electron microscopy observations found that there were inherent wavy wrinkles on the surface of a single layer of graphene, which is a possible reason for graphene to remain thermodynamically stable. Graphene is the thinnest but also the hardest nanomaterial in the world, with many unique physical properties. Its thermal conductivity is as high as 5300 W / m·K, its electron mobility at room temperature exceeds 15000 cm2 / V·s, and its resistivity is only about 10-6Ω·cm. Graphene has very broad application prospects, such as field emission sources and their vacuum electronic devices, thermal conductive materials / thermal interface materials, transparent conductive electrodes and solar cells.

[0003] In the prior art, the highly oriented self-assembly of graphene oxide is the core to achieve high thermal conductivity of graphene film, and graphene oxide microsheets with a monolayer rate of more than 90% are the key to achieve highly oriented self-assembly. Graphene oxide with a high monolayer rate is prone to agglomeration due to the effect of hydrogen bonds, and the solid content needs to be reduced to achieve homogeneous dispersion, but low solid content slurry will seriously reduce coating efficiency and significantly increase manufacturing costs. Summary of the invention

[0004] The purpose of the present invention is to provide a method for dissociating and dispersing a single-layer graphene oxide, aiming to solve the problem in the prior art that graphene oxide with a high monolayer rate is prone to agglomeration due to the action of hydrogen bonds, and the solid content needs to be reduced to achieve homogeneous dispersion, but the low solid content slurry will seriously reduce the coating efficiency and greatly increase the manufacturing cost.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for dissociating and dispersing a single-layer graphene oxide comprises the following steps: S1, mixing flake graphite with an oxidant, oxidizing it, and then subjecting it to an electrochemical intercalation and exfoliation treatment to obtain graphene oxide microsheets dispersed in an electrolyte for standby use; S2, adding the graphene oxide microsheets obtained in step S1 into an organic solvent containing a catalyst for catalysis to obtain a graphene oxide catalytic solution for standby use; S3, adding the graphene oxide catalytic solution obtained in step S2 into a reaction kettle, adding a dispersant, stirring, and obtaining a graphene oxide dispersion solution for standby use; S4, adding the graphene oxide dispersion solution obtained in step S3 into a reaction kettle, adding a solvent and a reducing agent in sequence, and performing stirring, high-speed shearing, and high-pressure homogenization treatment to obtain a graphene oxide slurry.

[0006] As a preferred solution of the present invention, the graphene oxide microflakes prepared in step S1 have a diameter of 5-20 μm.

[0007] As a preferred solution of the present invention, the intercalation agent used for the electrochemical intercalation stripping is a mixture of one or more raw materials selected from concentrated sulfuric acid, concentrated nitric acid, chlorosulfonic acid, and concentrated phosphoric acid in any proportion.

[0008] As a preferred solution of the present invention, the total water content in the intercalant is not higher than 2.5 wt %.

[0009] As a preferred solution of the present invention, the electrolyte in step S1 is prepared by mixing one or more raw materials of sulfuric acid, nitric acid, hydrochloric acid, sodium sulfate, potassium sulfate, sodium chloride, and ammonium nitrate in any proportion, and the solution conductivity of the electrolyte solution used is in the range of 100 μS / cm to 1000 S / cm.

[0010] As a preferred solution of the present invention, the catalyst is prepared by mixing one or more raw materials selected from ethanol, γ-mercaptopropyltrimethoxysilane, phenyltriethoxysilane, tetraethylammonium hydroxide, tetrahydrofuran and methanol in any proportion.

[0011] As a preferred solution of the present invention, the oxidant is potassium permanganate.

[0012] As a preferred solution of the present invention, the organic solvent is prepared by mixing one or more raw materials selected from the group consisting of xylene, ethanol, n-butanol, N-methylpyrrolidone and N,N-dimethylformamide in any proportion.

[0013] As a preferred solution of the present invention, the dispersant is a combination of one or more of polyvinyl alcohol, polyvinyl formal, hydroxymethyl cellulose, polyvinyl pyrrolidone and polyalkoxy ether ester.

[0014] As a preferred solution of the present invention, the solvent is made by mixing one or both of water and ethanol in any proportion.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. In the graphene oxide slurry prepared in the present invention, the monolayer rate is higher than 90%, and the solid content is significantly higher than the level of about 4wt.% in the industry; the graphene oxide is homogeneously dispersed without agglomerates; the viscosity of the graphene oxide slurry is effectively controlled within an ideal range, has good castability, and can realize automated pipeline transportation and coating.

[0016] 2. In the present invention, a catalyst is introduced before graphene is dispersed, so that the microsheets are stretched and there is no stacking or agglomeration between the microsheets. After dispersion, a reducing agent is introduced into the slurry to improve the fluidity of the slurry.

[0017] 3. In the present invention, the preparation of high-solid content, low-viscosity, and high-monolayer rate graphene oxide slurry is achieved through efficient dispersion processes such as bidirectional stirring, high-speed shearing, and high-pressure homogenization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 The present invention is a flowchart of a process for dissociating and dispersing a single-layer graphene oxide. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Example 1 See also Figure 1 , the present invention provides the following technical solutions: A method for dissociating and dispersing a single-layer graphene oxide comprises the following steps: S1, mixing flake graphite with an oxidant, oxidizing it, and then subjecting it to an electrochemical intercalation and exfoliation treatment to obtain graphene oxide microsheets dispersed in an electrolyte for standby use; The oxidant is potassium permanganate, and the mass ratio of potassium permanganate to flake graphite is 1:3; the oxidation time is greater than 3 hours; and the reaction temperature is controlled within the range of 31°C-39°C; Electrochemical intercalation stripping treatment has a high stripping efficiency. Under the action of an applied voltage, the anions dissociated from the electrolyte move toward the anode and then insert into the graphite layers, reducing the van der Waals force between the graphite layers. During the electrolysis process, water and anions decompose to produce gas, which promotes the expansion of graphite and stripping into flaky single-layer or few-layer graphene. The intercalation agent is one or a mixture of two or more of concentrated sulfuric acid, concentrated nitric acid, chlorosulfonic acid and concentrated phosphoric acid in liquid phase, and the total water content in the intercalation agent is not higher than 2wt%; after the flexible graphite is intercalated, the obtained product has unchanged shape and remains in a continuous state, and the mechanical and electrical properties are not deteriorated; The electrolyte is prepared by mixing one or more raw materials selected from sulfuric acid, nitric acid, hydrochloric acid, sodium sulfate, potassium sulfate, sodium chloride, and ammonium nitrate in any proportion, and the solution conductivity of the electrolyte solution used is in the range of 100 μS / cm to 1000 S / cm; In this scheme, a certain amount of sulfuric acid is used as the electrolyte. First, a constant voltage of 1 V is applied, and the electrolysis is carried out for 5 to 10 minutes, and then the voltage is adjusted to 10 V for 1 minute. The role of the low voltage is to wet the electrode and insert sulfate ions into the grain boundaries of graphite; the stripping product is redispersed in a dimethylformamide (DMF) solution and has good stability; after atomic force microscopy testing, the final few-layer graphene obtained has a sheet thickness of more than 65% less than 2 nm and an average sheet size of 5-20μm; using sulfuric acid as an electrolyte for electrochemical stripping has the advantages of high efficiency and speed, but the defect density of the produced graphene is high. At the same time, since sulfuric acid itself has a strong oxidizing property to graphite, and an oxidant is added, a certain amount of KOH can be added to the sulfuric acid solution to adjust the pH value of the electrolyte to obtain higher-quality graphene microsheets; S2, adding the graphene oxide microsheets obtained in step S1 into an organic solvent containing a catalyst for catalysis to obtain a graphene oxide catalytic solution for standby use; The catalyst is prepared by mixing one or more raw materials selected from ethanol, γ-mercaptopropyltrimethoxysilane, phenyltriethoxysilane, tetraethylammonium hydroxide, tetrahydrofuran and methanol in any proportion; The organic solvent is prepared by mixing one or more raw materials selected from the group consisting of xylene, ethanol, n-butanol, N-methylpyrrolidone and N,N-dimethylformamide in any proportion; By adding a catalyst before dispersion, the microsheets are stretched and there is no stacking or agglomeration between the microsheets. S3, adding the graphene oxide catalytic solution obtained in step S2 into a reaction kettle, adding a dispersant, stirring, and obtaining a graphene oxide dispersion solution for standby use; Wherein, the dispersant is a combination of one or more of polyvinyl alcohol, polyvinyl formal, hydroxymethyl cellulose, polyvinyl pyrrolidone and polyalkoxy ether ester; S4, adding the graphene oxide dispersion solution obtained in step S3 into a reaction kettle, adding a solvent and a reducing agent in sequence, stirring, high-speed shearing, and high-pressure homogenization to obtain a graphene oxide slurry; The solvent is one of water and ethanol or a mixture of the two raw materials in any proportion, and the reducing agent is hydrogen-rich water; By adding reducing agents and solvents after dispersion, the slurry fluidity is improved, making the subsequent stirring effect better and the mixing more obvious; During the stirring, forward and reverse bidirectional stirring is performed to make the stirring more thorough, thereby achieving the preparation of high solid content, low viscosity, and high monolayer rate graphene oxide slurry.

[0021] In a specific embodiment of the present invention, the graphene oxide slurry prepared by the present invention, after testing, has a monolayer rate higher than 90%, and a solid content significantly higher than the level of about 4wt.% in the industry, and the graphene oxide is homogeneously dispersed without agglomerates; the viscosity of the graphene oxide slurry is effectively controlled within an ideal range, has good castability, and can realize automated pipeline transportation and coating.

[0022] Specifically, the graphene oxide microflakes prepared in step S1 have a diameter of 5-20 μm.

[0023] Specifically, the intercalation agent used for electrochemical intercalation stripping is a mixture of one or more raw materials selected from concentrated sulfuric acid, concentrated nitric acid, chlorosulfonic acid, and concentrated phosphoric acid in any proportion.

[0024] Specifically, the total water content in the intercalant is not higher than 2.5 wt %.

[0025] Specifically, the electrolyte in step S1 is prepared by mixing one or more raw materials of sulfuric acid, nitric acid, hydrochloric acid, sodium sulfate, potassium sulfate, sodium chloride, and ammonium nitrate in any proportion, and the solution conductivity of the electrolyte solution used is in the range of 100 μS / cm to 1000 S / cm.

[0026] Specifically, the oxidizing agent is potassium permanganate.

[0027] Specifically, the catalyst is prepared by mixing one or more raw materials selected from ethanol, γ-mercaptopropyltrimethoxysilane, phenyltriethoxysilane, tetraethylammonium hydroxide, tetrahydrofuran and methanol in any proportion.

[0028] Specifically, the organic solvent is prepared by mixing one or more raw materials selected from the group consisting of xylene, ethanol, n-butanol, N-methylpyrrolidone and N,N-dimethylformamide in any proportion.

[0029] Specifically, the dispersant is a combination of one or more of polyvinyl alcohol, polyvinyl formal, hydroxymethyl cellulose, polyvinyl pyrrolidone and polyalkoxy ether ester.

[0030] Specifically, the solvent is one of water and ethanol or a mixture of the two raw materials in any proportion.

[0031] In the present invention, in the process of preparing graphene oxide slurry, by proposing parameter requirements on the graphene oxide microsheet structure, the preparation effect of single-layer graphene oxide with large sheet diameter and specific oxygen content is more significant, and at the same time, by introducing a catalyst before graphene dispersion, the microsheets are stretched, and there is no stacking and agglomeration between the microsheets. After dispersion, a reducing agent is introduced into the slurry to improve the fluidity of the slurry; the subsequent high-efficiency dispersion processes such as bidirectional stirring, high-speed shearing, and high-pressure homogenization realize the preparation of graphene oxide slurry with high solid content, low viscosity, and high monolayer rate. According to the surface detection, the monolayer rate in the graphene oxide slurry is higher than 90%, and the solid content is significantly higher than the level of about 4wt.% in the industry; the graphene oxide is homogeneously dispersed without agglomerates; the viscosity of the graphene oxide slurry is effectively controlled within an ideal range, has good castability, and can realize automated pipeline transportation and coating.

[0032] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for dissociating and dispersing a single-layer graphene oxide, characterized in that: The steps include: S1, mixing flake graphite with an oxidant, oxidizing it, and then subjecting it to an electrochemical intercalation and exfoliation treatment to obtain graphene oxide microsheets dispersed in an electrolyte for standby use; S2, adding the graphene oxide microsheets obtained in step S1 into an organic solvent containing a catalyst for catalysis to obtain a graphene oxide catalytic solution for standby use; S3, adding the graphene oxide catalytic solution obtained in step S2 into a reaction kettle, adding a dispersant, stirring, and obtaining a graphene oxide dispersion solution for standby use; S4, adding the graphene oxide dispersion solution obtained in step S3 into a reaction kettle, adding a solvent and a reducing agent in sequence, and performing stirring, high-speed shearing, and high-pressure homogenization treatment to obtain a graphene oxide slurry.

2. A method for dissociating and dispersing a single-layer graphene oxide according to claim 1, characterized in that: The graphene oxide microflakes prepared in step S1 have a sheet diameter of 5-20 μm.

3. A method for dissociating and dispersing a single-layer graphene oxide according to claim 2, characterized in that: The intercalation agent used in the electrochemical intercalation stripping is a mixture of one or more raw materials selected from concentrated sulfuric acid, concentrated nitric acid, chlorosulfonic acid and concentrated phosphoric acid in any proportion.

4. A method for dissociating and dispersing a single-layer graphene oxide according to claim 3, characterized in that: The total water content in the intercalant is not higher than 2.5 wt %.

5. A method for dissociating and dispersing a single-layer graphene oxide according to claim 4, characterized in that: The electrolyte in step S1 is prepared by mixing one or more raw materials selected from sulfuric acid, nitric acid, hydrochloric acid, sodium sulfate, potassium sulfate, sodium chloride, and ammonium nitrate in any proportion, and the solution conductivity of the electrolyte solution used is in the range of 100 μS / cm to 1000 S / cm.

6. A method for dissociating and dispersing a single-layer graphene oxide according to claim 5, characterized in that: The oxidant is potassium permanganate.

7. A method for dissociating and dispersing a single-layer graphene oxide according to claim 6, characterized in that: The catalyst is prepared by mixing one or more raw materials selected from ethanol, gamma-mercaptopropyltrimethoxysilane, phenyltriethoxysilane, tetraethylammonium hydroxide, tetrahydrofuran and methanol in any proportion.

8. A method for dissociating and dispersing a single-layer graphene oxide according to claim 7, characterized in that: The organic solvent is prepared by mixing one or more raw materials selected from the group consisting of xylene, ethanol, n-butanol, N-methylpyrrolidone and N,N-dimethylformamide in any proportion.

9. A method for dissociating and dispersing a single-layer graphene oxide according to claim 8, characterized in that: The dispersant is a combination of one or more of polyvinyl alcohol, polyvinyl formal, hydroxymethyl cellulose, polyvinyl pyrrolidone and polyalkoxy ether ester.

10. A method for dissociating and dispersing a single-layer graphene oxide according to claim 9, characterized in that: The solvent is one of water and ethanol or a mixture of the two raw materials in any proportion.

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